Hello Michael,

Yes, there are several studies—both within and outside Michigan—that explore the effects of mixing liquid urea with fulvic acid and humic acid on turfgrass, particularly cool-season species. Here's a summary of relevant findings from academic sources:

Key Findings from Research Studies

1. Reduction of Ammonia Loss

Study: Reduction of Ammonia Loss by Mixing Urea with Liquid Humic and Fulvic Acids

Institution: Universiti Putra Malaysia

Findings:

Mixing urea with humic and fulvic acids significantly reduced ammonia volatilization.

Treatments with both acids improved ammonium (NH₄⁺) retention and reduced nitrogen loss.

The high cation exchange capacity (CEC) of humic acids was key to their effectiveness. More information at this link:

(PDF) Reduction of Ammonia Loss by Mixing Urea with Liquid Humic and Fulvic Acids Isolated from Tropical Peat Soil

2. Improved Nutrient Availability

Source: University of Arizona Extension

Insights:

Humic and fulvic acids act as chelating agents, thereby enhancing the availability of essential micronutrients such as iron, zinc, copper, and manganese.

These acids may cause turf to turn green quickly, especially when combined with urea nitrogen. More information at this link:

soil amendments

3. Creeping Bentgrass Growth and Stress Tolerance

Study: Humic Substances and Their Influence on Creeping Bentgrass

Institutions: Clemson University & North Carolina State University

Findings:

Application of humic substances increased root dry mass and root dehydrogenase activity, indicating healthier root systems.

At higher concentrations (400 ppm), humic acid enhanced photosynthesis and stress tolerance under heat-stress conditions. More information at this link:

1999aug6.pdf

4. Coal-Derived Humic Substances

Study: Reducing Ammonia Loss from Urea by Mixing with Humic and Fulvic Acids Isolated from Coal

Findings:

Treatments with both humic and fulvic acids reduced nitrogen loss by up to 25% compared to urea alone.

Enhanced soil NH₄⁺ and NO₃⁻ levels and improved exchangeable cation profiles. More information at this link:

(PDF) Reducing Ammonia Loss from Urea by Mixing with Humic and Fulvic Acids Isolated from Coal

Practical Implications for Turfgrass Management

Cool-season turfgrass, such as Kentucky bluegrass or creeping bentgrass, may benefit from these mixtures through:

Enhanced nutrient uptake

Reduced nitrogen loss

Improved root development and stress resilience

Application Tips:

Use humic and fulvic acids in liquid form, alongside urea, for improved integration into the soil.

Monitor soil pH and CEC to optimize effectiveness.

Consider foliar versus root zone application, depending on the turf type and management goals.

I hope this helps!